Isla Fisher Is Spectacularly Miscast As Myrtle Wilson In The Great Gatsby

I know the rule in Hollywood is that the actors in a movie are always going to be incomprehensibly attractive, no matter how ugly or plain their characters are supposed to be. But I thought we were at least supposed to try for some verisimilitude when it came to adapting great literature, so I was holding Baz Luhrmann's The Great Gatsby to a higher standard. Except now he's gone and cast Isla Fisher as Myrtle Wilson, according to THR, and any scrap of hope I had that this would be more than beautiful people swanning around in flapper clothes has been lost entirely.

The cast already includes Leonardo DiCaprio as Gatsby, Carey Mulligan as his flame Daisy, Ben Affleck as her meanie husband Tom Buchanan, and Tobey Maguire as the fly-on-the-wall narrator Nick Carraway. All of these characters are relatively wealthy and privileged, so it makes some sense for them to be movie-star attractive. But Myrtle, the wife of an auto mechanic with whom Tom is having a fairly inexplicable affair, is distinctly, specifically plainer than all the rest. Here's how she's described in the book:

"She was in the middle thirties, and faintly stout, but she carried her surplus flesh sensually as some women can. Her face […] contained no facet or gleam of beauty, but there was an immediately perceptible vitality about her as if the nerves of her body were continually smoldering.

So, sure, Fisher is plenty vital, and always a welcome presence on the screen. And yes, she could conceivably gain weight to fit into Myrtle's curvy description. But I still can't possibly see her fitting the role, and wonder what on earth Luhrmann is thinking in casting her. I don't want to be one of those slavish fans of a book who objects to everything, but come on-- am I the only one who thinks there was a more logical casting decision to be made here?